Okami not only does what adventure games do best, but it also does things that you would not expect, and make them work.
At first glance one would say that the graphics in the game look kind of low quality, but in fact they are supposed to look like a traditonal japanese ink drawing. When keeping this in mind, its easy to tolerate the unusually thick black outlines and semi-abundance of sprites used in some places instead of polygons. Overall, they look very good.
Gameplay is pretty good. It combines Devil May Cry style combat with Zelda-like exploration, making it fun all the way through. You never get bored from running around in Shinshu field or finding demons to fight. There is plenty of Leveling up and upgrading weapons involved, similar to Final Fantasy or God of War.
If you have a ps2 or a wii, GET THIS GAME. it is one of the best adventure games ever.